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200-301 · Question #126

For what two purposes does the Ethernet protocol use physical addresses?

The correct answer is A. to uniquely identify devices at Layer 2 E. to allow communication between different devices on the same network. Ethernet physical (MAC) addresses are used to uniquely identify devices at Layer 2 and facilitate communication between devices within the same local network segment.

Submitted by katya_ua· Mar 5, 2026Network Fundamentals

Question

For what two purposes does the Ethernet protocol use physical addresses?

Options

  • Ato uniquely identify devices at Layer 2
  • Bto allow communication with devices on a different network
  • Cto differentiate a Layer 2 frame from a Layer 3 packet
  • Dto establish a priority system to determine which device gets to transmit first
  • Eto allow communication between different devices on the same network
  • Fto allow detection of a remote device when its physical address is unknown

How the community answered

(65 responses)
  • A
    94% (61)
  • B
    3% (2)
  • C
    2% (1)
  • F
    2% (1)

Why each option

Ethernet physical (MAC) addresses are used to uniquely identify devices at Layer 2 and facilitate communication between devices within the same local network segment.

Ato uniquely identify devices at Layer 2Correct

Each Ethernet network interface card (NIC) possesses a globally unique Media Access Control (MAC) address, serving as its distinct identifier at Layer 2 of the OSI model.

Bto allow communication with devices on a different network

Communication with devices on a different network relies on Layer 3 (IP) addresses and routing protocols, not solely on Layer 2 physical addresses.

Cto differentiate a Layer 2 frame from a Layer 3 packet

Ethernet addresses are part of a Layer 2 frame and do not serve to differentiate a Layer 2 frame from a Layer 3 packet; these are distinct protocol data units.

Dto establish a priority system to determine which device gets to transmit first

While Quality of Service (QoS) mechanisms can prioritize traffic at Layer 2, MAC addresses themselves do not inherently establish a system for determining transmission priority.

Eto allow communication between different devices on the same networkCorrect

MAC addresses are essential for direct communication among different devices residing on the same local area network (LAN) segment, ensuring that Ethernet frames are delivered to the correct recipient.

Fto allow detection of a remote device when its physical address is unknown

ARP (Address Resolution Protocol) is used to discover a physical address for a known IP address on the local network; the purpose of the MAC address itself is to uniquely address frames once known, not to facilitate remote device detection when unknown.

Concept tested: Ethernet MAC address purpose

Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet/17156-ethernet.html

Topics

#Ethernet#MAC addresses#Layer 2 addressing#LAN communication

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